A specific quantity of electricity, known as the rated power, is intended to be produced by solar systems and panels under ideal laboratory conditions. Solar panels may be unable to provide the rated power in actual use because of factors like temperature and light intensity.
It is typical for solar systems and panels to produce less energy than their rated capacity, and this is frequently due to lighting circumstances outside of ideal laboratory conditions.
A solar system's output may also be impacted by elements like the inverter's efficiency and the position of the panels. Therefore, it's critical to be realistic about predicted system output and appreciate that a solar system's output might not match its rated power.
Is it normal for solar systems and panels to have a lower output than the rated power?
Years ago, I was in charge of a solar installation company. Sometimes after an installation, we would get a call from a customer, and they would say something like, “Hang on, I just had a 5kw solar system installed. It’s a beautiful sunny day. It’s the second day that my system is on, and I look at the monitoring app, and it only produces 3.9 kWh. Why am I only getting 3.9 kWh of output when I have a 5 kW system? Should I not get 5kWh in output when it’s perfectly sunny?
Then, I always felt the system handover procedure or the salesperson left an important piece of information off in explaining to the customer how solar works.
The reality in Australia, in many areas, you might only have 500, 600 or 800 Watts on a given day as the light intensity hits that panel. So if only 80% of the thousand watts of light shines on the panel, the solar panel will only produce an output of roughly 80%. In our 400Watt panel example, this would be 320Watts.
So please do not think that because you have a 5kw solar panel system, every hour of the day will produce 5 kW hours of output. The actual solar system output will very much depend on the light intensity.
In Europe, for example, in Germany, some regions only experience a 400W per square meter light intensity (irradiation), a 10 kW solar system output would only be half of what a system in North Queensland will produce per year.
Also, a 10 kW system in Cairns, which is an area of high solar irradiation, will, on average, produce 17,382 kWh of electricity output per year, while in Hobart, with much lower light intensity, the same 10 kW system will produce only 12,359 kWh, a 28.9% lower production. So where you live will affect the return on investment and solar system output numbers.
Solar system output
Therefore, if a 400-watt panel produces 320 to 350 Watts in good conditions within Australia, you are getting a good result. On the other hand, you rarely get 5kW output from a 5kW solar panel system, except on certain days, with certain clouds where cloud reflection artificially lifts light level numbers for short periods.
For warmer times of the year in the middle of the day, you should probably expect a peak of around 4.2-4.3 kW of output from a 5 kW solar panel system for a few hours in the middle of the day.
The message to take away from this FAQ is – that don’t stress if you do not get the full capacity output; there is most likely nothing wrong with your system.